This K23 research and training award advances the long-term goal of improving treatment outcomes and reducing transmission of HIV among HIV-infected drug users. The proposed training and research plans will enable the PI to develop the skills needed for an independent research career in the area of illicit drug use and HIV adherence intervention. The objective of this application is to develop skills in implementation science, behavioral intervention development and evaluation with drug using populations, and in-depth qualitative data analysis to accelerate refinement and effective implementation of interventions for HIV-infected drug users. Multiple comorbidities such as drug use and HIV act synergistically to produce poorer health outcomes and increase morbidity, mortality, and transmission of HIV. Consequently, effective and sustainable interventions adapted to drug users to improve antiretroviral medication adherence and reduce risk behaviors are urgently needed. Drug users present unique treatment challenges compared with other HIV-infected populations, including lower rates of adherence and inferior treatment outcomes. Additionally, interpersonal factors, including social support, negative patient-provider interactions, and socioeconomic challenges present significant barriers to adherence. Thus, the generalizability of current adherence interventions to drug users is limited, and there is a pressing need for efficacious interventions adapted to HIV-infected drug using populations. This application addresses this gap by being the first to adapt and test the acceptability and efficacy of a combined adherence and brief motivational intervention for HIV-infected drug users. Specifically, the intervention will augment the established Life Steps adherence intervention to include: (1) a tailored Life Steps module addressing the unique needs of illicit drug users, aimed at improving medication adherence; (2) a brief Motivational Interview to address drug use and other risk behaviors; and (3) two follow-up booster sessions. A three-phase, top-down research approach to adapt, refine, and pilot test the intervention will be conducted. Phase 1 will include focus groups with HIV-infected drug users currently prescribed antiretroviral medications and individual interviews with community-based clinicians. Phase 2 will include manual development, therapist training, a pilot trial, in-depth qualitative interviews, and further manual revisions. Phase 3 will include a small, 2-armed (intervention vs. health education control) randomized controlled trial with 60 HIV-infected drug users. Feasibility, acceptability, and preliminary indication of improvement in antiretroviral adherence and reduction in drug use will be examined at 1-, 3-, and 6-month follow-ups. To enable the PI to pursue this long-term research agenda, she will work with experienced mentors to build three areas of expertise: (1) proficiency in qualitative research methods and analysis; (2) skills in intervention development and evaluation with illicit drug using populations; (3) expertise in advanced longitudinal data analysis; and (4) implementation science. This K23 proposal addresses a key priority in HIV treatment science, and it will fully prepare the PI for an independent research career as an HIV intervention scientist.